An MEMS (Micro-Electro-Mechanical System) scanning apparatus is formed by processing a substrate made of silicon or the like by using a semiconductor process. The MEMS scanning apparatus is typically composed of a mirror coupled to a base via a spring portion, and a light source for emitting a beam toward the reflecting surface of the mirror (see, e.g., Patent Document 1).
In such an MEMS scanning apparatus, the mirror reflects the beam from the light source, while it is driven by the resilient force of the spring portion when a force is applied thereto.
Specifically, the mirror is designed to swing rotationally or linearly under the effect of the resilient force of the spring portion. As a result, a reflected beam from the mirror performs a scanning operation in accordance with the movable range of the mirror thus swinging.
Patent Document 1: JP-2003-302586A
Although an MEMS scanning apparatus as described above is simple in structure and small in size, it is of a swing type using the resilient force of the spring portion so that the scan angle of the mirror, i.e., the swing angle thereof is small.
FIG. 9 is a view showing a schematic cross-sectional structure of a typical prior-art MEMS scanning apparatus. As shown by the arrow Y1 in FIG. 9, a mirror 10 rotationally swings when a force such as an electrostatic force is applied thereto.
At this time, a beam LB from a light source 50 is caused to perform a scanning operation by rotationally swinging the mirror 10. To increase the angle θ2 of the range scanned by the reflected beam LB, i.e., the scan angle θ2 of the beam, the swing angle of the mirror 10 should be increased.
To increase the swing angle of the mirror 10, however, a high-voltage circuit for generating a larger force such as a larger electrostatic force becomes necessary. When the mirror 10 is caused to swing greatly, the mirror 10 interferes with a structure located thereunder, such as a support substrate, so that the swing angle of the mirror 10 is restricted disadvantageously.
Thus, the rotationally swinging type of the MEMS scanning apparatus has such problems as the need of the high-voltage circuit and the restricted swing angle resulting from the interference of the mirror with the adjacent structure. Furthermore, a linearly swinging type of the MEMS scanning apparatus also has the similar problems.